Monday, May 9, 2016

High capacity valves on the face of
O'Shaughnessy Dam release spring
snowmelt to the upper Tuolumne River.

With a relatively healthy snowpack in the upper Tuolumne watershed in Yosemite National Park and spring snowmelt well underway, the SFPUC Hetch Hetchy Water & Power division began ramping up releases from O'Shaughnessy Dam to the upper Tuolumne River on Sunday, May 8th, for the first ecological pulse flow since the California drought began in 2012. Flows will reach 6,500 cubic feet per second (cfs) by Wednesday, May 11th.

The releases are designed to achieve a number of experimental ecological objectives, including managing foothill yellow-legged frog reproduction, inundating unique wetlands in the Poopenaut Valley, and mobilizing fine sediment, sand, and gravels to improve trout and foothill yellow-legged frog habitat.

Wetlands in the Poopenaut Valley that haven't seen significant flooding since 2011 will be fully inundated by the peak release of 6,500 cfs, providing valuable information on how wetlands may recover from several years of drought.

The sediment mobilizing releases will serve to move silt and sand that has increased in the upper Tuolumne River since the 2013 Rim Fire. Fine sediment can fill the spaces between gravels and cobbles, allowing stream side vegetation to encroach into the river channel and "fossilize" the loose gravel and cobble patches that trout, foothill yellow-legged frogs, and other aquatic life need to successfully reproduce.

Scientists from the SFPUC, Yosemite National Park, and UC Davis are monitoring the releases and will be studying their ecological effects throughout the spring and summer. Data from this work will be used to update and refine analyses and river management strategies described in the Draft O'Shaughnessy Dam Instream Flow Management Plan.

Friday, April 8, 2016

The April snow survey is in and the upper Tuolumne is at 89%, much better than the single digits we experienced a year ago. To hear more about the snowpack, the hydrologic outlook, spring high flow releases, and more, join us at the Upper Tuolumne River Stakeholder Group meeting on April 29th in Moccasin. A draft agenda will be available within two weeks. RSVP at wsears@sfwater.org.

Wednesday, March 16, 2016

The interdisciplinary Yosemite National Park (NPS) Looking Downstream Project is designed to better understand the physical processes and ecology of the Tuolumne River between O’Shaughnessy Dam and the western boundary of Yosemite National Park. The project goal is provide information the SFPUC can use to manage O’Shaughnessy Dam environmental water releases to more closely replicate natural hydrology for the benefit of water-dependent ecosystems downstream.

The 2014-2015 water year was dry: precipitation was approximately 58% of average. April 1st and May 1st snow water equivalent, however, were at record lows (9% and 2% of average April 1st, respectively) continuing a historically unprecedented drought in central California. Hydrology studies in spring 2015 focused on monitoring low flow conditions. These low flows precluded any experimental releases from O'Shaughnessy Dam.

Vegetation-related fieldwork in Poopenaut Valley documented the rapid spread of non-native common mullein within and adjacent to the seasonal pond on the north side of the river. Although the 2013 Rim Fire may have contributed to the spread of common mullein in this area, it is most likely related to the nearly continuously dry conditions in the pond over the past few years.

Spring bird surveys in Poopenaut Valley consisted of area searches, point counts, spot mapping, nest searches, and color banding. A cumulative total of 240 individual birds from 38 species were observed. Spot mapping determined breeding territories of the four target riparian focal species (Warbling Vireo, Yellow Warbler, Song Sparrow, and Black-headed Grosbeak) to elucidate their habitat-use patterns. Data collected during spot mapping and nest searching in 2011–2015 were used to calculate arrival, initiation of breeding, and fledging dates for the target riparian focal species. In 2015, NPS found 68 nests, which is substantially more than in previous year. Nest failure rate in Poopenaut Valley seemed unusually high; of the 68 nests found, 60% failed and 25% had unknown fates.

Bat studies have identified an impressive biodiversity of bat species inhabiting Poopenaut Valley from spring 2011 through late summer 2015. Bat detection frequencies decreased in 2015 to levels comparable to pre-2014 levels. The only species with marked increases were western mastiff bat and big brown bat at the south site. Species richness decreased slightly in 2015 at both sites and was fairly consistent with pre-2014 numbers. Seasonal patterns in species richness were also consistent with previous years at both sites.

The 2015 Yosemite National Park Looking Downstream Project report can be accessed here.

Since 2007 the SFPUC has conducted fisheries monitoring in the Hetch Hetchy Reach of the upper Tuolumne River. In 2014, the SFPUC asked Stillwater Sciences (in collaboration with McBain Associates) to take a fresh look at our existing approach and provide recommendations that would increase sampling efficiency and statistical robustness. Stillwater's recommendations included sampling shorter sites with an increased number of passes, thus providing a slight increase in efficiency, and over time, a more reliable statistical basis for understanding the relationship among environmental variables, O'Shaughnessy Dam releases, and trout populations. The recommendations and their implementation during our fall 2014 snorkel survey effort are described in this report.

Thursday, February 4, 2016

The 2013 Rim Fire burned over 257,000 acres within the Stanislaus National Forest and Yosemite National Park, becoming the third largest wildfire to date in California. To help provide an understanding of potential post-fire ecological changes in the Hetch Hetchy Reach of the upper Tuolumne River, the SFPUC has funded annual monitoring of fine sediment, large wood, and riparian vegetation encroachment. Results from the first year of monitoring are now available here and in the UTREP library.

Wednesday, March 4, 2015

The spring upper Tuolumne River stakeholder group meeting is scheduled for April 3rd 11am – 3pm in the Moccasin Admin building. Lunch will be provided by Hetch Hetchy Water and Power. A draft agenda will be circulated shortly. If you haven’t done so already, please RSVP to wsears@sfwater.org at your earliest convenience if you are planning to attend.

Wednesday, June 18, 2014

The Forest Carbon research team at NASA Ames Research Center has launched the Rim Fire Tracker online map viewer to help track regenerating vegetation areas within the 2013 burned severity classes. The maps feature changes in current (2014) Landsat 8 NDVI (normalized difference vegetation index) compared to last October's (post-burn) NDVI. The map layers will be updated every month with a new Landsat NDVI difference product. Subsequent image analysis of the vegetation community in regenerating areas will be added to this map viewer over time. Tools are provided to zoom to a location, identify values, and download map layers. Subsequent image analysis of the vegetation community in regenerating areas will be added based on the methods published previously by Potter et al. (2012).

The draft O'Shaughnessy Dam Instream Flow Management Plan is available for download via links provided below. The plan is comprised of a main document (211 pp) and 13 technical appendices (619 pp). The main document is intended to provide a thorough description of proposed future instream flow releases for O'Shaughnessy Dam and a summary of analyses used to develop the plan. In-depth, discipline-specific technical descriptions of analytical methods and results are provided in the appendices document for more technical readers.

Saturday, April 5, 2014

Whitewater boating access for the Cherry and Lumsden runs on the Tuolumne River is open for the season. Access is by shuttle only and free, mandatory permits are required via the Groveland Ranger Station. For more information on white water and other recreation on the Stanislaus National Forest, see the Stanislaus National Forest recreation update. Boaters are asked to watch for hazards associated with the Rim Fire such as landslides and fallen trees.

Friday, April 4, 2014

A rockfall occurred just east of Wapama Falls on the North side of Hetch Hetchy Reservoir on March 31st, covering approximately 600 ft of the Wapama Falls trail. The falls can still be reached from the west, but the trail is closed just east of the falls. The National Park Service does not currently have an estimated date for reopening the closed section of trail.

Friday, March 28, 2014

National Park Service and US Forest Service fire crews completed a 57 acre prescribed fire near O'Shaughnessy Dam today. The combination of recent rains, minimal snowpack, and slightly unsettled weather made for ideal prescribed fire conditions; these conditions typically don't exist in March due to snowpack and wet fuels. The fire treated vegetation and fuels around the buildings and other infrastructure near O’Shaughnessy Dam, and was designed to reduce surface and “ladder fuels” that allow ground fire to leap to the tree canopy and cause crown fires. The treated area will offer a “fuel break” for firefighters to safely protect structures at the O’Shaughnessy Dam. The area burned with low intensity during the 2013 Rim Fire.

Thursday, March 27, 2014

Seasonal high flow water releases, or pulse flows, are increasingly used to simulate natural hydrology and manage river habitats downstream of dams and diversions. Beginning March 23rd and continuing for eight weeks, about 1 percent of the Colorado River’s waters will be released into the Colorado River Delta in Mexico. The release is part of a five-year pilot project designed to restore the delta environment and is part of an amendment to a decades old treaty between the United States and Mexico on management of Colorado River water. Read more online.

Tuesday, January 21, 2014

The first jointly scheduled Southern Sierra Fire and Yosemite Hydroclimate Workshop will be held April 22-24, 2014 in Yosemite Valley. The workshop is focused on developing an integrated view of the physical landscape, climate effects, hydrology, and fire regimes of the Sierra Nevada. This workshop was rescheduled from the original date back in October 2013 due to the federal government shutdown. To register, visit the California Fire Science Consortium website.

Tuesday, January 14, 2014

The USGS has installed a new stream gage near Ward's Ferry Bridge, at the upstream end of Don Pedro Reservoir, to monitor Rim Fire-related water quality parameters. The gage currently records stage, water temperature, conductance, turbidity, dissolved oxygen, and pH. The gage is funded by Modesto and Turlock irrigation districts, and the SFPUC.

Friday, January 10, 2014

Yosemite National Park's 2011-2012 update report for the "Looking Downstream" project is available for download in the library.

Looking Downstream is a long-term interdisciplinary study designed to better understand the physical processes and ecology of the mainstem Tuolumne River between O’Shaughnessy Dam and the western boundary of Yosemite National Park, with a focus on the biologically diverse Poopenaut Valley. The project provides critical information used to manage environmental water releases from O’Shaughnessy Dam.

Wednesday, November 27, 2013

To support new methods of valuing watersheds and the ecosystem services they provide, the San Francisco Public Utilities Commission funded Earth Economics to develop a preliminary assessment of the economic impact of the Rim Fire. The preliminary assessment includes loss estimates related to air quality, carbon sequestration, flood protection, erosion control, biological control, water filtration, pollination, habitat and biodiversity, property and aesthetic values, and recreational values. This initial effort provides support to federal, state, and local governments in justifying more robust, long-term investments in watersheds and forest health. The assessment is available here.

Tuesday, November 12, 2013

For over 5 years the SFPUC and NPS have collaborated on experimental flood releases from O'Shaughnessy Dam to support development of a new instream flow management plan for the upper Tuolumne River between the dam and Early Intake. The releases have primarily been conducted to test flow thresholds for sediment transport and Poopenaut Valley wetland inundation. Similar flood release experiments have been underway on other rivers; among the most widely reported are the releases from Glen Canyon Dam into the Grand Canyon on the Colorado River.

The Glen Canyon Dam Adaptive Management Program began in 1997 as an effort to use high flow releases to manage sediment (primarily sand) for the benefit of backwater habitats that provide key fish and wildlife habitat, reducing erosion of archaeological sites, restore and enhancing riparian vegetation, and restoring sand bar beaches for recreational boating and camping. The releases maintain water supply obligations by releasing less water during other parts of the year, mimicking pre-dam flows and water temperatures.

This week, the Glen Canyon program is conducting a second high flow experimental release from Glen Canyon Dam under a protocol approved in 2012. The protocol calls for conducting more frequent high flow experimental releases from the dam timed to occur following sediment inputs to the Colorado River from downstream tributaries. Large amounts of sediment were deposited over the summer due to major rainstorms. The volume of sediment available is about three times larger than the volume available during the last high flow release in the fall of 2012.

Tuesday, October 15, 2013

Due to the continuing federal shutdown, federal stakeholders and partners will likely be unable to attend or provide updates at the scheduled stakeholder meeting on October 18th. Given the importance of their participation to UTREP and the interests of upper Tuolumne stakeholders we are rescheduling the stakeholder meeting for November 15th, 2013, pending confirmation with federal agencies. An update will be provided when the meeting is finalized.

Friday, September 27, 2013

UC Davis has done it again, this time with "gigapixel" imagery of the Clavey River confluence, before and after the Rim Fire. A gigapixel image contains more than 100 times the information captured by a typical 10 megapixel digital camera. Gigapixel imagery is a product of NASA, Google, and Carnegie Mellon University efforts to develop imaging technologies for NASA Mars rovers. The technique has been used in Yosemite Valley to document rockfall hazards, and as UC Davis has illustrated, gigapixel imagery has potential for broad application in watershed and river management to document changing landscapes over time.

Thursday, September 26, 2013

Several UC Davis Center for Watershed Sciences staff received permission from the Stanislaus National Forest to hike into the mainstem Tuolumne River near the Clavey River confluence to investigate the fate of river monitoring gear after the Rim Fire. Here's what they found.

Tuesday, September 24, 2013

Quick note: the Fall 2013 meeting of the Upper Tuolumne River Stakeholder Group will take place on October 18th in Moccasin. An agenda is currently being developed. If you'd like to attend, RSVP to wsears@sfwater.org.

Wednesday, September 18, 2013

The Southern Sierra Fire and Hydroclimate Workshop is scheduled for October 1-4, 2013 at the Yosemite Lodge in Yosemite Valley. This event combines, for the first time, the annual Yosemite Hydroclimate workshop and the Wildland Fire Science workshop. The workshop focuses on an integrated view of the physical landscape, climate effects, hydrology, and fire regimes of the Sierra Nevada. Given the recent Rim Fire, which burned portions of the Stanislaus National Forest and Yosemite National Park, this and future workshops should provide a useful forum for tracking fire science efforts in the coming years. More information and registration details can be found here.

Friday, August 30, 2013

Some incredible videos are coming out of the firefighting efforts on the Rim Fire. Although most are readily available via Twitter and other social media, we'll be sharing a few that provide some perspective on one of the largest fires in California history. Here's one from Yosemite National Park.

Tuesday, April 30, 2013

NASA and Cal Tech's Jet Propulsion Laboratory are conducting a pilot project this spring, known as the Airborne Snow Observatory (ASO), to more precisely estimate the volume of water present in the snowpack within the Hetch Hetchy watershed. The project utilizes frequent aircraft flights and specialized sensors to develop water volume estimates that are potentially more accurate than existing methods, and provide data on a weekly basis versus the existing monthly snow surveys. The techniques developed in the pilot project may eventually help reservoir operators better manage reservoir operations and UTREP ecological releases. Read more about the Airborne Snow Observatory Project in this Washington Post article, this LA Times story, and this KQED radio bit.

The agenda and presentations from the April 19th, 2013 Upper Tuolumne River Stakeholder Group meeting are now available online. The Fall stakeholder meeting is scheduled for October 18, 2013 in Moccasin.

Saturday, February 9, 2013

The pre-development or "natural" state of a river system provides important context for river ecosystem management and rehabilitation: What did the river system look like before major development? What is the "natural" hydrologic regime? How are species adapted to the natural hydrograph? These are all questions that the UTREP is investigating in the upper Tuolumne, and are common to many other river ecosystem management efforts.

On January 18, 2013, the Delta Science Program and the UC Davis Center for Aquatic Biology & Aquaculture (CABA) hosted a seminar to explore how we use, and what we mean by, a natural hydrograph or unimpaired flows. The seminar focuses on the California Bay-Delta, but is relevant to work on the upper Tuolumne and elsewhere.

Friday, January 11, 2013

Yosemite National Park has released the Tuolumne Wild and Scenic River Comprehensive Management Plan and Draft Environmental Impact Statement (Tuolumne River Plan/DEIS). The plan describes management alternatives (including a preferred alternative) for the Tuolumne River Wild & Scenic river corridor within Yosemite National Park, including portions of the UTREP study area. Studies by UTREP collaborators, including the NPS Looking Downstream Project efforts, contributed to development of the plan. The upper Tuolumne River was designated by the U.S. Congress in 1984 under the Wild and Scenic Rivers Act. The park has also released the Merced River Plan, which addresses Wild & Scenic River management within the Merced River corridor, including Yosemite Valley.

Tuesday, December 4, 2012

Earlier this year, the SFPUC completed a report on the potential changes (increase or decrease) in Tuolumne River inflows to Hetch Hetchy Reservoir with anticipated changes in climate. The study used modeled temperature and precipitation data from a range of previously modeled climate change scenarios. While the likelihood of any particular climate future was not assessed, and the report doesn't seek to address potential water supply impacts of climate change, the simulated 2040, 2070, and 2100 hydrologic conditions show a progressively altered snow and runoff regime in the watershed. Snow accumulation is reduced and snow melts earlier in the spring. Fall and early winter runoff increases while late spring and summer runoff decreases, and these changes become more significant at the later time periods. Total runoff is projected to decrease under the climate change scenarios evaluated, in some cases marginally and others significantly. The consequences of these potential changes for UTREP efforts is unknown at this time, but will be considered in our ongoing instream flow work.

Sunday, December 2, 2012

This past spring, UC Davis researchers installed time lapse cameras, water stage recorders, and temperature monitoring equipment in both the mainstem Tuolumne River (regulated by Hetch Hetchy Project facilities - particularly Holm Powerhouse) and the Clavey River (an unregulated tributary to the Tuolumne) near their confluence. Video gurus at UC Davis then layered the time lapse video, stage, and temperature data of both rivers, providing a visual comparison of temperature and hydrology dynamics in the regulated and unregulated streams. This work is part of a larger UC Davis effort to learn more about how tributaries and stream confluences affect hydrology and geomorphology. Watch the video in HD on Vimeo for best effect, and to learn more about how the video and data were compiled.

Tuesday, May 29, 2012

From April 30 to May 4, 2012, the SFPUC hosted the Pacific Northwest Watershed Managers (PNWM) group on a tour of the SFPUC water system, from the San Francisco Peninsula to Hetch Hetchy. The group consists of watershed managers from the six largest unfiltered municipal water supply systems along the Pacific coast of North America, and was created to facilitate the exchange of information about programs,
policies, and best management practices. Materials discussed during the tour are available for viewing and download below.

Please note: we use Google Docs to host files online. Smaller files will be previewed in Google Docs, while larger files can only be downloaded. If a file is displayed in Google Docs, but you'd rather download it, go to the "File" menu and select "Download original". In some cases, Google can't preview the file and will say so; choose "Download" to download the file to your computer. If you are having issues, email wsears@sfwater.org.

Wednesday, April 25, 2012

As the spring unfolds and late rains continue to fall, it's clear this is not the dry year it could have been. However, the rains came too late to make up for the mostly precipitation-free winter. The good news is this provides another opportunity to test the snowmelt management strategies being developed for O'Shaughnessy Dam to benefit the Poopenaut Valley wetlands and the rest of the Tuolumne River ecosystem. This year, operational tests will focus on managing available snowmelt spill to fill the Poopenaut Valley pond while also providing good conditions for foothill yellow-legged frogs. Dry years provide the best opportunity to benefit the small foothill yellow-legged frog population present upstream of Early Intake. In wetter years the upper mainstem Tuolumne features higher and more variable snowmelt flows that can last into the summer. Wet year high flows can delay egg-laying or scour egg clutches, and are challenging for egg and tadpole development, as they likely were even under natural conditions. Dry year snowmelt spill flows are designed to peak early and provide more stable flow conditions for egg laying and tadpole development. Filling the Poopenaut pond will provide good conditions for benthic macroinvertebrates, chorus frogs, garter snake, bats, and other wildlife that depend on the pond ecosystem over the remainder of spring and into early summer.

Planned snowmelt management hydrograph.

Flow releases from O'Shaughnessy Dam will remain at current levels through Friday, April 27 to accomodate biological monitoring work, but will increase on Saturday to 200 cfs and possibly slightly higher thru Monday. Flows will ramp up on Tuesday, with a peak on Wednesday (May 2) of 4100 cfs. The peak will be timed for mid-day Wednesday to allow the highest flow to pass boaters in the Lumsden reach went they are off the water in the evening and allow for observation at O’Shaughnessy Dam and the Poopenaut Valley overlook during daylight. The current plan is to ramp down to 250 cfs by Thursday afternoon; however flows may stay higher if needed to manage snowmelt inflows.

Monday, March 26, 2012

UC Santa Cruz and NPS researchers recently published their work on Poopenaut Valley groundwater modeling and monitoring in the Journal of Hydrology. The researchers monitored experimental high flow releases from O'Shaughnessy Dam to assess the relative importance of inundation versus groundwater rise in establishing and maintaining riparian wetland conditions to determine how restoration benefits might be achieved while reducing total flood discharge. The observations helped to calibrate a numerical model that was used to test scenarios for controlled flood releases.

Modeling of the groundwater–wetland system suggests that inundation of surface soils is the most effective mechanism for developing wetland conditions, although an elevated water table helps to extend the duration of soil saturation. Results of the study will be incorporated into flow recommendations being developed for O'Shaughnessy Dam by UTREP.

We've just uploaded NPS update reports on ecological monitoring in the Poopenaut Valley for 2009 and 2010. In 2009 and 2010, NPS scientists continued to conduct extensive monitoring of wetland and meadow hydrology, birds, vegetation, and benthic macroinvertebrates. New work in these two reports includes groundwater modeling by UC Santa Cruz and bat surveys conducted by NPS.

Wednesday, March 21, 2012

The next meeting of the Upper Tuolumne River Stakeholder Group is set for April 13, 2012 from 11am - 2:30pm at the Moccasin Administration Building (map). View or download the agenda here. If you plan to attend the Stakeholder Group meeting, please email Bill Sears at wsears@sfwater.org.

Tuesday, November 8, 2011

Thanks to all who attended our recent stakeholder meeting in Moccasin.
Meeting materials from the November 4, 2011 stakeholder meeting are now
available for viewing and download here. Our next meeting is tentatively scheduled for April 13, 2012.

Friday, October 28, 2011

The Sacramento-Shasta Chapter of the Wildlife Society will be hosting their Natural Resources Symposium on November 2, 2011. The symposium will feature talks on climate change, birds and mammals, mitigation and restoration, vernal pools, and regulated flow effects.

The regulated flow effects session will feature topics relevant to our work on the Tuolumne, including an overview of UTREP, a talk by UTREP collaborator Sarah Kupferberg on regulated flows and frogs, and a presentation by UC Davis scientist Sarah Yarnell on suitable snowmelt recession rates below dams.

Registration info can be found on the Sacramento-Shasta Chapter's website.
View or download the agenda here.

Friday, October 21, 2011

The next meeting of the Upper Tuolumne River Stakeholder Group is set
for November 4, 2011 from 11am - 3pm at the Moccasin Administration Building
(map). View or download the agenda here.

Water Year 2011 turned out to be the second wettest year on record for the Upper Tuolumne, providing ample spill volumes for testing flow thresholds and snowmelt management techniques at O'Shaughnessy Dam. At the stakeholder meeting, Yosemite National Park will update the group on Tuolumne Wild & Scenic planning and Looking Downstream, we'll hear about new SFPUC collaborations to improve snowmelt forecasting, get updated on O'Shaughnessy Dam flow recommendations, and learn about efforts by UC Davis researchers to study the "lower" Upper Tuolumne River.

If you plan to attend the Stakeholder Group meeting, please email Bill Sears at wsears@sfwater.org.

Tuesday, September 27, 2011

The Resources Management and Science Division of Yosemite National Park will host the annual Yosemite Hydroclimate Meeting on October 6-7, 2011 at the Yosemite Lodge. The meeting is
open to the public and features talks on hydrology and climate
relevant to management of Yosemite. Two talks will focus on recent high flow experiments during spring snowmelt releases downstream of O'Shaughnessy Dam as part of UTREP.

Thursday, August 11, 2011

The latest update from Adam Mazurkiewicz at Hetch Hetchy Water and Power...

We are seeing continued recession of flows all across the Sierra. What a runoff year! I think the last few weeks have offered a great flow range for boating on the mainstem, but a late start for the Cherry Creek Run. That is just the hand Mother Nature has dealt us. As I mentioned in last week’s update, starting 8/10 expect typical releases into Cherry Creek. So for the remainder of the season we will be on the “normal” boating schedule, with HHWP release totaling ~1100 cfs for 4 hours and arriving at Lumsden (Meral’s Pool) around 9am (see Dreamflows for full schedule). Given it has been such a wet and cool year the additional accretions may make the usual flows slightly higher.

In GENERAL following the “rafting hours" there may be continued elevated flows, ~750-850 cfs from the HHWP project. Flows in the night and early morning (from HHWP) may be in the 550-650 cfs. I know there are camps that “dry” out following the boating release, so take this into consideration. The timing will vary depending on where you are along the river. On Sundays, flows will be in the lower range in the “off-rafting” hours. These flows may vary, but I wanted to share the “general” schedule with folks, so no one is surprised.

I do want to remind folks that August 17th and 30th are scheduled maintenance days and HHWP is utilizing the time. There have been inquiries regarding the releases following Labor Day. There will not be boating flows possible after Labor Day due to maintenance work.

If there are any changes/updates/issues I will send out a notice. Enjoy the last few weeks of the boating year!

Tuesday, August 2, 2011

Here's the latest update for Upper Tuolumne River flow conditions and Hetch Hetchy Project releases from Adam Mazurkiewicz, hydrologist for Hetch Hetchy Water and Power (HHWP).

Recently, thunderstorms have brought flows up quickly on the mainstem of the Tuolumne as measured by the Tuolumne at Grand Canyon gage. These thunderstorms have been over the Tuolumne and Merced watersheds, while Cherry and Eleanor have remained storm free. The additional precipitation and stunning longevity of the snowpack have caused some changes in the forecast and operations.

Starting August 1st, there will be additional water below Kirkwood Powerhouse (KPH), while releases below Holm Powerhouse (HPH) will be reduced to ~400-500 cfs throughout the day. Expect 700 cfs additional water below KPH. Given the spill occurring at Hetch Hetchy the flow at Lumsden on August 1st will be 2400 - 2600 cfs.

Tuesday August 2nd: Flows will be similar to Monday and the 2400-2600 cfs range should hold, but may fall to the lower end as spill from Hetch Hetchy may recede.

Wednesday August 3rd: Flows will be dependent on the inflow recession to Hetch Hetchy and any thunderstorms which may occur. Snowmelt should continue to be receding, but there will be flows for boating in a range of 2100 – 2600 cfs.

Thursday August 4th: Flows to allow for Cherry Creek run boating are right near the threshold given the uncertainty of spill at Hetch Hetchy. This estimate cannot be guaranteed but is based on the best current forecast and operation information so please check current flow conditions using the USGS gage stations or the Dreamflows estimate (these notices are also posted on the Dreamflows website). There will be boating flows at Lumsden between 2000 and 2500 cfs.

For the Cherry Creek run specifically, flows at the confluence are a total of what is below Hetch Hetchy, Eleanor and Cherry, HPH and additional water from KPH. Cherry and Eleanor are at minimum seasonal release (15 and 20 cfs) and are scheduled to remain at those rates unless thunderstorms generate significant inflows. Both these reservoirs are near their capacities. KPH is scheduled to contribute ~700 cfs. Spill from Hetch Hetchy will continue to follow natural recession as part of a UTREP flow experiment. It is expected spills from Hetch Hetchy will be between 800 and 1000 cfs on Thursday (total = approx. 1550-1750 cfs). Release from HPH between the hours of 0100 and 0900 hrs will be ~150 cfs, at 0900 to 1200 hrs releases will go up to ~250 cfs, at 1200 hrs releases will go up to 350 cfs. That brings the early day flow estimate to be between 1800 and 2000 cfs (which includes an estimate of accretions) going up to 1900 to 2100 cfs at 0900 hrs. Spill at Hetch Hetchy will control the variation from that estimate.

These estimates are subject to change due to mountain thunderstorms or unscheduled shutdowns. If you're out on the river, check gages for latest flow information.

Monday, July 18, 2011

Scott Ligare and Josh Viers of UC Davis have posted results of research into the effects of climate change on whitewater boating in the Sierra on UC Davis' California WaterBlog. Under mild warming (+2° C or 3.6°F), changes in runoff are likely to increase the average number of boatable weeks per year. However, under extreme warming (+6° C or 10.6° F) there will be a significant decrease in the average boatable weeks per year across the Sierra Nevada. These results vary depending upon location and gradient of the run. Read more on the UC Davis California WaterBlog.

In order to gain a more complete understanding of the ecology downstream of O'Shaughnessy Dam, we have been studying bird populations in Poopenaut Valley since 2007. Having characterized the breeding bird community and detected about 100 species in total, this year (2011) we are vigilantly observing the timing of when migratory birds arrive, set up and defend their territories, and initiate nesting. In Poopenaut Valley, nest searching provides a more in-depth look at how the changing water level affects breeding birds in terms of their reproductive success and the timing of nest building, egg hatching, and fledging.

NPS biological technician, Matt Brady, conducts a bird survey
on the north side of the Tuolumne River in Poopenaut Valley
(Sarah Stock photo).

Since bird surveys began this year on April 27, we have detected over 80 bird species in the Poopenaut Valley study area. In addition to the regular, resident species that are present year-round, we have observed many north-bound spring migrants. Pulses of Warbling Vireos and Black-headed Grosbeaks, two of our Riparian Focal Species, were noticeable amongst the flocks of migrating Bullock’s Orioles, Yellow-rumped Warblers, Chipping Sparrows, and Red-winged Blackbirds. By the first week of May, the first pair of Yellow Warblers, another Focal Species, had set up territory. Although the nesting season seems to be somewhat delayed this year because of colder temperatures, late May nest searching yielded nests of American Robin, Bullock’s Oriole, Cassin’s Vireo, House Wren, and Yellow Warbler. Further, several pairs of Song Sparrows have been exhibiting nesting behavior, though we have not confirmed any of their nests.

In some regards the delayed nesting season is good; once the spring snowmelt begins and high flow releases from O’Shaughnessy Dam start to flood the riparian vegetation, any active nests along the Tuolumne River would likewise flood. If birds nest after the beginning of the planned high flow releases, they will only be able to place their nests in locations where they will be less likely to flood. Environmental flow recommendations being developed under UTREP for O’Shaughnessy Dam will likely include measures that should prevent nesting in low lying riparian areas that may be subsequently flooded by spring snowmelt releases.

An interesting aspect of early season breeding surveys is the possibility for finding unusual species that are still migrating toward breeding grounds farther north. This year, we have added seven new species to the total number of species detected: American Coot, American Crow, Common Yellowthroat, Gray Flycatcher (six individuals), Virginia Rail, Wood Duck, and Yellow-headed Blackbird. All of these species are considered rare in Yosemite National Park, which suggests that Poopenaut Valley is an important stopover for birds during spring migration.

Tuesday, July 5, 2011

Two backpackers died crossing the Wapama Falls bridge on June 29 during late season high flows on Falls Creek, which feeds Wapama Falls and empties into Hetch Hetchy Reservoir. Falls Creek reached its highest flow of the snowmelt season on the 29th due to a late Alaskan cold front bringing heavy rain to the high country and accelerating snowmelt.

Wapama Falls bridge spans a steep and dynamic portion of Wapama Falls with massive boulders and swift flows, even during low flow periods. Please use caution and common sense when crossing swift water. Read more at LAist.

There are about 1,240 bat species worldwide, 24 of which are native to California. In Yosemite National Park, 17 bat species are known to occur and five are special status species that have experienced statewide declines. While population declines in California are mostly caused by habitat degradation outside of the park, this serves to highlight the importance of parkland as a refuge for bat species and means that bats may be more sensitive to management activities within the park.

The Poopenaut Valley is a unique area downstream of O’Shaughnessy Dam on the Tuolumne River in Yosemite National Park. With its open wet meadows, riparian vegetation, and seasonal pond, the valley provides important habitat for bats. Bats are essential in maintaining ecosystem health by controlling insect populations through nighttime foraging. Most bat species forage either over water or within the adjacent riparian zone, where plant and insect productivity is higher than in drier upslope areas.

National Park Service (NPS) biologists are incorporating the study of bats into ongoing UTREP and Looking Downstream Project efforts in the Poopenaut Valley. The seasonal pond occupying the north side of the valley supports numerous aquatic and terrestrial species. When the pond fills in winter and spring due to snowmelt and runoff from winter rains, an entire food web develops. As the pond fills and the temperature increases, aquatic vegetation begins to grow, and aquatic and terrestrial insect populations begin to develop, which in turn provide food for garter snakes, Pacific chorus frogs, and bats.

Using advanced acoustic monitoring techniques, park biologists are working to understand how bats use the Poopenaut Valley pond and other habitats in the valley. The monitoring effort uses a system of specialized acoustic detectors to match bat echolocation calls to known recordings. In this work, NPS biologists are looking at how bats use the valley during the year and are measuring the amount of bat foraging that takes place in relation to the amount of water present in the seasonal pond.

Data from a pilot study in 2010 and preliminary surveys through mid-May of 2011 indicate that 12 different bat species occur in Poopenaut Valley, including four California Species of Special Concern (Townsend’s big-eared bat, pallid bat, spotted bat, and western mastiff bat). The other eight bat species detected include hoary bat, silver-haired bat, western pipistrelle, Mexican free-tailed bat, California myotis, Yuma myotis, long-eared myotis, and fringed myotis.

This research will be integrated into other work in the Poopenaut Valley to characterize the food web response (including bats) to varying water levels. Since filling of the pond each year is related to flows released from O’Shaughnessy Dam to the Tuolumne River, this research will aid in developing a better understanding of how water releases affect bat populations and the ecology of the seasonal pond, providing guidance to the NPS and SFPUC in making informed flow management decisions.

Thursday, June 2, 2011

On May 31, NPS Biological Technician Matt Brady observed a second year male Scott's Oriole (Icterus parisorum) in Poopenaut Valley. This species has not previously been reported within Yosemite National Park and thus brings the park's bird list to 261 species. It is the first sighting in the park and the second within surrounding Tuolumne County. Scott's Oriole's are native to the southwestern United States and Mexico. NPS biologists working in the Poopenaut Valley have seen a number of unusual species for the park this spring, including Gray Flycatcher, American Coot, Common Yellowthroat, Yellow-headed Blackbird, Wood Duck, and Green-tailed Towhee.

Tuesday, May 24, 2011

Cool weather continues to preserve the snowpack and moderate inflows to Hetch Hetchy Reservoir, which has been allowed to rise above 300,000 acre-feet to prepare for UTREP high flow releases this week. Releases began yesterday (May 23rd) as part of a slightly modified schedule.

In order to confirm Poopenaut Valley wetland inundation flow thresholds, bench releases were made today at 3,300 cfs and 3,700 cfs. These will be followed by releases at 4,800 cfs (May 25 @ 08:00) and 5,700 cfs (May 25 @ 15:00). The peak release of 8,500 cfs will begin on May 26 @ 08:00 and begin to ramp down on May 28 @ 08:00. Following the peak, releases will be ramped down to 5,700 cfs to support Poopenaut Valley inundation. These releases are being monitored by equipment in Poopenaut Valley and by NPS staff as part of Yosemite National Park's Looking Downstream Project.

Releases are currently 3,700 cfs from O’Shaughnessy Dam, 700 cfs from Kirkwood powerhouse, 1,900 cfs from Cherry Creek, 900 from the Middle and South Fork Tuolumne, and about 200 cfs of accretion flow. Dreamflows is a few hours behind recent changes (due to travel time) and is at 6,400 cfs and on its way to 7,400 cfs. See realtime flow links at right for current flow information.

Flow estimates (plus or minus 500 cfs) for Lumsden are:

May 25: 7,400 cfs in the morning, rising through the day to 9,400 cfs around 6 pm
May 26: 9,400 cfs in the morning, rising to 12,200 cfs around 1 pm
May 27: 12,200 cfs all day
May 28: 12,200 cfs in the morning, decreasing to 10,100 cfs around 3 pm.
May 29: 10,100 cfs in the morning, decreasing to 9,400 cfs around 3 pm

Releases from O'Shaughnessy Dam will hold constant from May 30 through at least June 3, and the approximately 9,400 cfs at Lumsden will rise or fall based on the tributary contributions and snowmelt. If warmer weather follows the cold Memorial Day weekend, the ~9,400 cfs will continue to June 8.

Tuesday, May 10, 2011

Due to cool temperatures and some highly variable weather, inflows to Hetch Hetchy Reservoir have dropped significantly. In the last 4 days at 8,500 ft in the Tuolumne watershed, conditions have gone from 65F daytime highs at 8,500 feet to 3” of new snow at 8,500 ft. Cool conditions are expected to persist through May 17th. The low inflows mean that Hetch Hetchy operators will not have adequate levels of water storage in the reservoir to implement the "test drive" of ecological high flow releases as planned next week. Instead, the planned high flow test drive will be delayed by a week; Hetch Hetchy operators plan to begin ramping on Sunday, May 22.

Here's the current plan for the releases at O'Shaughnessy Dam (OSD) and resulting flows at Lumsden:

May 12 - 22: OSD release of 1,400 cfs. Lumsden flows will be approximately 5200 when combined with Cherry, Kirkwood powerhouse, and Middle and South Forks flows;

May 23 -24: OSD release of 3,300 cfs. Lumsden flow will be approximately 7100 cfs;

May 25: OSD release of 4,800 cfs. 8,800 cfs at Lumsden;

May 26: OSD release of 5,700 cfs. 9700 cfs at Lumsden;

May 27 – 29: OSD release of 8,500 cfs. 12,500 cfs at Lumsden;

The length of the 8,500 cfs high flow release will depend on weather and inflows. Wetland inundation bench flows will be released after the peak, however the timing will again depend on weather. High flows at Lumsden (>9,000 cfs) are likely to continue – assuming normal spring/warming weather – through at least June 8. We'll provide updates here as the snowmelt season unfolds.

Wednesday, May 4, 2011

This has been a very wet winter with recent snow survey results indicating the snowpack in the Upper Tuolumne watershed at 184% of average May 1st snow conditions. Currently, the snow line is near 5600 feet and has melted on south and west slopes up to approximately 6400 ft; above 6400 feet the snow coverage is 100%. Warm temperatures over the last week have been melting this low elevation snow and generating streamflows in the watershed. Over all, SFPUC hydrologists believe over 500,000 acre-feet of excess runoff ("spill") is likely to occur over the next 2-3 months at O'Shaughnessy Dam.

As discussed at the April 8 stakeholder meeting, draft UTREP flow recommendations for O'Shaughnessy Dam include high flow releases during the snowmelt season to meet sediment transport and Poopenaut Valley wetland inundation objectives. This year, the SFPUC and NPS will take those recommendations for a "test drive" to help identify any potential operational issues. Beginning May 15th, operators at O'Shaughnessy Dam will begin high flow releases, starting with test wetland inundation "benches" at 3300, 3700, 4800, and 5700 cfs.

High flow release from O'Shaughnessy Dam in 2009. (W. Sears photo)

These releases will be monitored by equipment in the Poopenaut Valley and NPS staff will take photos to confirm inundation of wetland surfaces. A peak release for sediment transport of 8500 cfs is targeted for May 19th and 20th, followed by a 5700 cfs bench or a continued 8500 cfs release if it is necessary to control Hetch Hetchy reservoir elevations. Although variable weather conditions could require changes to this plan, the "test drive" will provide us with a valuable opportunity to evaluate the operational procedures needed to implement a new set of flow recommendations at O'Shaughnessy Dam.

Wednesday, April 27, 2011

When trying to understand river health, aquatic biologists often look not at fish, but rather fish food: benthic macroinvertebrates (or BMI). BMI are effective integrators of physical, chemical, and biological processes and are valued as indicators of river ecosystem health due to various BMI species occupying primary, secondary, tertiary, and higher-level consumer levels in riverine food webs. They are, in turn, a critical food resource for a variety of vertebrates, including fish.

Over the last three years, Jeff Holmquist and Jutta Schmidt-Gengenbach of the University of California White Mountain Research Station have been studying BMI in the river reach downstream of O'Shaughnessy Dam as part of the Looking Downstream Project and UTREP. The goal is to develop an understanding of BMI species diversity and abundance in the Tuolumne, and characterize how BMI assemblages change with flow. Current and future work will focus on food web dynamics and long term changes in BMI assemblages resulting from implementation of ecosystem-based environmental flow recommendations for O'Shaughnessy Dam.

Jeff and Jutta recently completed the first survey in their fourth year of sampling with assistance from dam operators at Hetch Hetchy Water and Power who were able to reduce releases from O'Shaughnessy Dam to allow access to the river channel.

Top left: Larva of predaceous diving beetle from pond habitats. The larvae of some species can reach almost two inches in length. Adults are smaller, but are also aquatic predators. (Holmquist photo)

Top right: Drift net in place below O'Shaughnessy Dam in the Tuolumne River. The net catches insects that enter the water column. BMI floating downstream (known as "Drift") are a natural phenomenon and an important source of food for fishes. In addition to BMI, surprisingly large numbers of terrestrial insects are found in drift samples. A one-hour sample can include close to 1,000 insects and 125 species. (Holmquist photo)

Bottom right: A backswimmer, found in pond habitats. These insects swim on their backs and have one pair of legs specialized as oars. Backswimmers have a stinging beak that is used in prey capture. The beak is visible in the photo and runs along 3/4 of the length of the body. (Holmquist photo)

Bottom left: Tossing a throw trap in the Poopenaut pond, 3 miles downstream of O'Shaughnessy Dam. The trap encloses a known volume of water column and associated substrate, and animals are removed with a bar seine. The device is effective at catching fauna that might avoid other collecting devices. The pond has a high level of diversity and abundance, sometimes over 1,000 insects per square meter. (Schmidt-Gengenbach photo)

Taken while flying West over Yosemite. The area around Yosemite National Park is a major corridor for East-West flights, posing a challenge for Yosemite National Park staff attempting to manage soundscapes in wilderness areas of the Park. Visible are three of the higher elevation reservoirs of the Hetch Hetchy Project, including (left to right) Cherry Reservoir, Lake Eleanor, and Hetch Hetchy Reservoir. The dark abyss just right of center is the Tuolumne River Gorge. The Early Intake area is just off the bottom left corner. Click on the photo for a larger version. (W. Sears photo)

Friday, February 4, 2011

On October 3-4, 2010 the Hetch Hetchy area experienced a severe electrical storm. During one 24-hour period, the Hetch Hetchy Reservoir rose approximately 25 feet and the foot bridge near Wapama Falls was destroyed due to falling rock and flood flows from Falls Creek. Yosemite National Park's current plan is to repair and open the bridges by April 2011 in time for early spring backpackers and hikers.

Sunday, January 30, 2011

Due to scheduling conflicts including the Salmonid Restoration Federation conference, the date of the next stakeholder meeting has moved from March 25 to April 8, 2011. We hope everyone can make this new date. Meeting details will be emailed to participants ahead of the meeting. Please email Bill Sears (wsears@sfwater.org) if you plan to attend.

Friday, January 14, 2011

Last week Yosemite National Park hosted the California/Nevada Amphibian Population Task Force Meeting in Yosemite Valley. The meeting was well attended and brought together some of the foremost experts in western amphibian populations. The two days of presentations at the Yosemite Lodge provided some valuable insights into the recent declines and conservation efforts underway for imperiled amphibians. The meeting ended with a field tour of the UTREP and Looking Downstream projects by SFPUC and NPS staff including Greg Stock, Yosemite park geologist (shown above presenting to participants on O'Shaughnessy Dam).

The meeting and field trip provided a unique opportunity for scientists with the SFPUC, McBain & Trush, the NPS, and others working on developing new environmental flow recommendations for O'Shaughnessy Dam under the UTREP project to obtain critical input on methods and results that have been used to quantify the magnitude, duration, frequency, and timing of flows needed to support amphibians (particularly foothill yellow-legged frog) in the Tuolumne River downstream of O'Shaughnessy Dam.

Input gained from the meeting will be incorporated into our current studies and will be reflected in the final draft flow recommendations report due in the first half of this year.

Monday, November 1, 2010

The newest installment of Yosemite Nature Notes by Steve Bumgardner is now on YouTube. This latest episode focuses on the Maclure and Lyell glaciers, which form the headwaters of the Tuolumne River, and features Greg Stock (Park Geologist with Yosemite National Park), Pete Devine (Naturalist at the Yosemite Conservancy), and mountain guide Josh Helling.

About the Program

The Tuolumne River is located on the west slope of the Sierra Nevada in central California. With headwaters in Yosemite National Park, the Tuolumne flows westward 150 miles to its confluence with the San Joaquin River in California's Central Valley.

The UTREP monitors river ecosystem conditions and develops recommendations for river management downstream of Hetch Hetchy Project facilities to support broad river ecosystem values, while maintaining water supply reliability for 2.6 million San Francisco Bay Area customers and providing clean hydropower for San Francisco municipal facilities.